Spawn coins on random objects

As stated in the title,I want to spawn coins(collectibles) on random generated objects at a random interval,how could I do that?I have tried imagepoints but got nowhere.

<img src="http://s8.postimg.org/5wj1587lh/ransom.jpg" border="0" />

This would do it.

bertie Booster That font. Why?

Why? Because years ago I found it softened the staccato syntax of several languages and now I'm older because it's a habit and easier to read without my glasses. <img src="smileys/smiley1.gif" border="0" align="middle" />

bertie Booster I guess you do have a fair point.

It just brings up memories of Comic Sans and every time it's been misused in serious context... >_>

Thank you Bertie,it seems I have a lot to learn about events :)

But one more thing,I want the coin to spawn everytime that particular block appears on the screen and only spawn once.

then use either:

block => on Created

or

block => Is on-screen

Trigger once while true

Thank you very much :D a few more problems to solve and I can get to the next step of the game -The shop-